What causes me to have word hallucinations when reading, i read things and think it says one then then go back and reread and its different, why?

Confusion: I would not call what you described word hallucinations. Hallucinations is perceiving something that doesn't exist. I am sort of confused over what your problem is. Please clarify if it makes one sense when you first read something but then it changes when you re-read it or you think you read one word when in fact it is a different one.